Date of Award
Master of Science (MS) in Biology
Japanese river bamboo (Pleioblastus simonii, ‘medake,’‘kawadake’) is an ecologically important species of temperate bamboo native to Japan. This species is widely known and historically important in Japanese rural farm life. Based on morphological data, Japanese river bamboo is classified in Pleioblastus section Medakea (Poaceae: Bambusoideae) along with five other Japanese species, which are collectively considered to represent a phylogenetically distinct lineage. However, recent studies suggest that Japanese river bamboo may have arisen as a result of previously undetected hybridization (i.e., cryptic hybridization), while also calling into question the diversity of section Medakea. The role of hybridization in natural plant populations has been studied since the 1950s; however, little is known about this phenomenon in the evolution of bamboos. Species of Pleioblastus share an issue common to bamboo taxonomy in that they exhibit overlapping variation in leaf and stem characteristics, making them difficult to identify based on morphology alone. One potential factor contributing to, and exacerbating, this issue is cryptic hybridization. The objective of this study was to analyze molecular data, including amplified fragment length polymorphism (AFLP) and nuclear DNA (nDNA) sequence data, to test the hypothesis that P. simonii is a species of hybrid origin. The results provide compelling evidence in support of this hypothesis, while also suggesting that ongoing diversification has obscured bamboo ancestry. Moreover, these findings highlight the importance of using up-to-date analytical v techniques from population genetics and phylogenetics to shed light on how to navigate the complexities of bamboo taxonomy. This study provides an example of reticulate evolution in the origin of plant diversity and helps to reveal why molecular data are important tools for plant taxonomy and systematics.